| In the practical production,dairy cows are fed high concentrated diets which commonly induce subacute ruminal acidosis(SARA).Additionally,dairy cows are frequently subjected to mastitis and metritis.Under the circumstances,the endotoxin(or lipopolysaccharide,LPS)increases within the cow and in the mammary epithelial cells,which will induce oxidative stress,negatively affecting the health and productive performance of dairy cows.To explore effective solutions and to meet the requirement of antibiotic-free animal husbandry,this study selected dandelion extract with the characteristic of anti-oxidation as a potential alternative to antibiotic.We firstly investigated the inhibitory effect of dandelion extract on LPS induced oxidative stress in bovine mammary epithelial cells and its mechanism in vitro.Then the in vivo study was conducted to verifiy the effects of dandelion extract on the oxidative stress in dairy cows under high concentrate diet.This study consisted of three different experiments:1.Effect of LPS with different levels on the oxidative stress in bovine epithelial cells.This study investigated oxidative stress and the consequent DNA damage induced by lipopolysaccharide(LPS)in bovine mammary epithelial cell line MAC-T cells.Cells were cultured for 48 h with different LPS levels(0,0.1,0.5,2.5,12.5,and 100 ng/mL).The results showed that:(1)Cell viability was negatively correlated with LPS concentrations.(2)The production of reactive oxygen species increased in a dose-depend manner.(3)Cellular concentrations of oxidative damage markers were positively correlated with applied LPS concentrations.(4)Total antioxidant capability and the activity of superoxide dismutase(SOD)increased with increasing LPS concentrations.2.Dandelion Extract Alleviated Lipopolysaccharide-induced Oxidative Stress through the Nrf2 Pathway in Bovine Mammary Epithelial Cells.This study was aimed to investigate the antioxidative effects of dandelion aqueous extract(DAE)on LPS-induced oxidative stress and the mechanism of DAE as an antioxidant to alleviate the oxidative stress through the nuclear factor erythroid2-related factor 2(Nrf2)pathway in the bovine mammary epithelial cell line MAC-T cells.The cells were cultured for 48 h in six treatments including control(without LPS and DAE),LPS(100 ng/mL),DAE10(100 ng/mL LPS and 10 ?g/mL DAE),DAE50(100 ng/mL LPS and 50 ?g/mL DAE),DAE100(100 ng/mL LPS and 100?g/mL DAE),and DAE200(100 ng/mL LPS and 200 ?g/mL DAE),respectively.The results showed that:(1)Cell viability was reduced by LPS,and the adverse effect of LPS was suppressed with the supplementation of DAE.(2)Lipopolysaccharide induced oxidative stress through enhancing reactive oxygen species(ROS)production,resulting in increases of oxidative damage markers' concentrations;while 10 and 50 ?g/mL DAE alleviated the LPS?induced oxidative stress via scavenging cellular ROS and improving antioxidant enzyme activity.(3)The upregulation of antioxidative gene expression in DAE treatments was promoted through activating the Nrf2 signaling pathway,with DAE at a concentration of 50?g/mL exhibiting the highest effect.3.Effects of dandelion extract in promoting production performance and reducing mammary oxidative stress in dairy cows fed high-concentrate diet.The purpose of this study was to investigate the effects of rumen bypass dandelion extract on lactation performance,immune index,and mammary oxidative stress on lactating dairy cows fed high-concentrate diet.The study used complete randomized block design,and initial milk production,somatic cell counts and parities were set as block factors.Sixty Holstein with similar health condition and lactating period(70 ± 15 d)were divided into three groups,and 20 replicates per group.The treatments included LCD group(low-concentrate diet,concentrate :forage = 4 : 6),HCD group(high-concentrate group,concentrate:forage = 6:4),and DAE group(dandelion aqueous extract group,HCD group with 0.5% DAE).Experimental period was 35 d,and cows were fed three times in the morning,afternoon and night with free water.The results showed that:(1)The milk production in HCD and DAE groups were significantly higher than LCD group since WK4,and the milk quality were different during the experiment period.(2)The p H value in HCD group were significant differ fromLCD and DAE group.(3)In WK2 and WK4 of the experiment period,the somatic cell counts of dairy cows in HCD group were signicantly hgher than DAE group.The white blood cells,lymphocytes and percentage of lymphocytes were significantly higher in HCD group than LCD group.(4)Serum concentration of 8-hydroxy-2'-deoxyguanosine(8-OHd G)and protein carbonyl(PC)in HCD group were significantly higher than LCD group.Activity of Catalase(CAT)in LCD and DAE group was stronger than HCD group.(5)The correlation analysis revealed significantly positive correlations between plasma LPS concentration and serum concentrations of 8-OHd G,PC,and malondialdehyde(MDA),and significantly negative correlations between plasma LPS concentration and activities of CAT and SOD.(6)Compared with HCD and DAE groups,m RNA expression of ??? and ? casein and acetyl Co A carboxylase in bovine mammary epithellial cells were significanly higher in LCD group,and m RNA expression of fatty acid synthase and stearoyl COA desaturase in LCD group were significantly higher than HCD group.(7)Compared with LCD and HCD groups,m RNA expression of Nrf2 was significantly higher in DAE group,and m RNA expression of cystine/glutamate transporter and NAD(P)H quinone oxidoreductase 1 in DAE group were significantly higher than HCD group.Overall,LPS induced oxidative stress in a dose-dependent manner in b MECs.Meanwhile,LPS stimulated the antioxidative defense which was enhanced with increasing LPS levels.However,the enhanced antioxidative defense could not offset the LPS induced damage to cellular biomolecules in b MECs.DAE acted as an effective antioxidant to inhibit LPS?induced oxidative stress and as a potential inducer of the Nrf2 signaling pathway.Feeding high-concentrated diet could increase milk yield of dairy cows,but the milk quality,rumen homeostasis,and antioxidative capability were adversely affected.The supplementation of DAE in high-concentrated diet enhanced antioxidative capability through activation of the Nrf2 regulatory factor and improved rumen homeostasis and production performance. |
PDF Full Text Request